Apparatus and method for mounting and removing tyres on and from respective wheel rims

ABSTRACT

An apparatus for mounting and removing a tyre on and from a respective rim comprises: an element for moving a bead of the tyre in order to insert/remove the bead into/from a respective groove in the rim, the element comprising a tool connected to a respective supporting arm for moving the bead; a rotatable support for the rim, in such manner as to turn the rim and the tyre about a corresponding longitudinal axis of the rim; at least one sensor associated with the supporting arm for measuring the mechanical strain applied to the bead of the tyre when the latter is mounted on, and removed from, the rim.

BACKGROUND OF THE INVENTION

This invention relates to an apparatus and a method for mounting andremoving tires on and from respective wheel rims.

As is known, apparatuses for mounting and removing tires on and fromrespective wheel rims are equipped with a rim supporting element that issuitably power driven to turn the rim during mounting or removal of thetire.

Usually, the rim supporting element is positioned with its axis vertical(that is, directed substantially in the direction of application of theweight force) or, alternatively, with the axis horizontal.

It should be noted that this invention relates to machines for mounting(and removing) the tires, without any limitation as to the orientationof the supporting element.

For brevity and simplicity, however, this description will refer to thecase where the supporting element is positioned with its axis verticalin such a way as to turn the wheel about a longitudinal axis of rotationoriented along said vertical axis.

Above the supporting element, there is a set of tools designed toposition the tire bead (that is, the annular edge of the tire) atpredetermined positions on the rim.

It should be noted that a tire has two beads, corresponding to the twoannular ends (or edges) of the tire itself.

Each bead has a head portion, oriented radially, and a lateral portion.

Prior art tools for mounting and removing tires on and from wheel rimsinclude, for example, a shaped element (for mounting) and a lever or aclaw (for removing) which are designed to be inserted between the beadand the rim in such a way as to position the bead at a predeterminedposition relative to the rim, in particular to push a first portion ofthe bead between the annular outer edges of the rim at a respectivegroove (during mounting) or to extract the bead from the rim and keep itin an extracted position relative to the rim groove (during removal).

Next, the rim is turned about its longitudinal axis so that the tool(which is held still while the rim is rotated) slides along at least apart of the circumference of the bead in such a way as to prise theentire bead inwards (during mounting) or outwards (during removal) overthe edge of the rim.

In addition, during mounting, a pressure disc is used to push a sidewall of the tire towards the opposite side wall.

During removal, on the other hand, the pressure disc is used to detachthe tire bead from the rim (in effect, during use, the tire becomes veryhot, causing the rubber to vulcanize, thereby making the bead adhere tothe wheel rim). The bead pressure disc, connected to one end of anoperating arm, is therefore also known as bead loosener.

The pressure disc may also be used as a further aid during tiremounting.

For example, when mounting the tire on the rim, the pressure disc (orbead loosener) is usually used to facilitate correct positioning of thebead relative to the rim.

When mounting very rigid or large tires, a pivoting clamp known by thetrade name of “Tucano” is also used. This clamp also holds the tire beadin place relative to the rim so as to minimize tension during mountingoperations (that is, the mechanical strain the tire bead is subjected towhile it is being fitted to the wheel rim).

The clamp consists of a gripper designed to hold the edge of the rim ata zone of the rim where the bead has already been pushed onto the rim.Under the gripper there is a flat part that presses the side wall of thetire near the bead. This flat part is pivotally mounted so that itremains in contact with the tire as the latter moves.

It should be noted that the rim forms a first and a second seat (in theform of annular grooves) for receiving a first and a second bead duringuse of the wheel. The seats are located at opposite lateral ends of therim.

The rim also has an annular groove or channel running round the middleof it.

This annular groove is in the form of a recess designed to receive atleast one portion of the tire bead temporarily during mountingoperations.

In effect, at least during an initial stage of the mounting operation,the axis of the tire is inclined with respect to the axis of the rim. Inthis situation, a first portion of the bead (or rather, of one of thetwo beads) is on the outside of the rim, held by the mounting/removaltool, while a second portion of the same bead (the portion diametricallyopposite it) is inside the rim channel, allowing the tire to be moved ina direction perpendicular to the rim axis, towards the mounting/removingtool.

This, as is known, facilitates tire mounting by reducing the mechanicalstrain the bead is subjected to.

In light of the above, the engagement tool consisting of the abovementioned clamp is designed to push one side of the tire, close to thebead, so as to keep the bead inside the channel in the zone of the beaddiametrically opposite the portion of the bead that interacts with themounting/removing tool.

The clamp is used together with a rim guard fitted to the edge of therim to prevent damage to the bead as it moves over the sharp edges ofthe rim.

In effect, when mounting the tire on the rim, the bead is subjected tomechanical strain that often leads to tire damage. That is because thebead is subjected to radial strain (bead compression), axial strain(bead lifting) and tangential strain (bead pulling, due to thefrictional component). All these types of mechanical strain on the bead,if they exceed certain limits (specified by tire manufacturingassociations and automobile constructors) may lead to serious tiredamage.

In this regard, it must be stressed that the risk of damage to the beadis particularly serious if it occurs during mounting because, once thetire has been mounted, the damage, if any, is not visible before thetire is used.

Further, the problem is felt particularly strongly on account of the useof run flat tires, that is, tires designed to resist the effects ofdeflation. Thus, in the event of a failure, a long time might passbefore the driver realizes the tire is damaged.

In fact, tire manufacturers now tend to make tires harder and with theshoulder lower down: this worsens the problem of damage to the tireduring mounting and removal.

To overcome this drawback, sensors such as extensometers applied to thetool or to the bead loosener are used, as is known from patent documentIT1274552.

However, this solution does not allow accurate and reliable measurementof the mechanical strain the tire bead is subjected to during mountingand removal.

In effect, the solution makes it possible to measure only the strainthat results in deformation of the tool (that is, of the bead loosener).A great deal of the strain applied the bead is subjected to, however, isabsorbed by the elasticity of the tool mounting structures. Moreover,the flexibility of the tools is limited and variable in time.

Another technical solution is known from patent document IT1263799.

This solution relates to a tire removing machine comprising a pair ofarms located on opposite sides of the wheel and movable towards eachother to abut the sidewalls of the tire so as to detach the bead fromthe rim (in practice, the arms are used as two bead looseners).

In this solution, the arms are equipped with sensors (torque meters ingeneral, extensometers in particular designed to measure the pressureapplied by the arms to the sides of the tire).

The pressure applied by the arms, however, is not converted into orreferable to mechanical strain acting on the bead.

This solution cannot therefore be used to obtain really useful andeffective information on the mechanical strain applied to the bead andpotentially able to damage the bead.

A further technical solution concerning an apparatus for servicing tiredwheel for motor vehicles is already known from document EP1479538.

In this solution, the apparatus comprises a rotatable motor-drivensupport for the positioning of the tired wheel. The rotatable support isconnected to the motor by a mechanical clutch which is used todisconnect the rotatable support from the motor, automatically andmechanically, when a critical load value, consisting of the mechanicalstrains applied to the tired wheel for assembling or disassembling it,is reached.

Moreover, this solution comprises an encoder designed to control theangular position of the rotatable support so that the encoder defines aposition sensor directed to verify when the clutch is operative.

However, also this solution does not allow accurate and reliablemeasurement of the mechanical strains the tire bead is subjected toduring mounting and removal, nor allows the monitoring of the trend ofsaid strains.

SUMMARY OF THE INVENTION

In this context, the technical purpose which forms the basis of thisinvention is to propose an apparatus and a method for mounting andremoving tires on and from respective wheel rims and which overcome theabove mentioned disadvantages.

In particular, this invention has for an aim to provide an especiallyreliable apparatus and method for mounting and removing tires on andfrom respective wheel rims that enables to make available useful data todetect and possibly prevent cases of tire bead damage.

Another aim of the invention is to provide an apparatus and method formounting and removing tires on and from respective wheel rims that makesit possible to mount and remove any tire without the risk of damagingtire beads.

The technical purpose and aims stated above are substantially achievedby an apparatus and method for mounting and removing tires on and fromrespective wheel rims, comprising the technical features set out in oneor more of the appended claims.

Thus, the apparatus and method according to the invention allow tires tobe mounted and removed on and from respective rims with the possibilityof measuring the mechanical strain applied to the tire bead while thelatter is deformed so it can be coupled/uncoupled to/from the rim.

In particular, the apparatus according with the present inventioncomprises:

-   -   a movement element for moving a bead of the tire in order to        insert/remove the bead into/from a respective groove in the rim;    -   means for supporting and moving the rim, designed to        rotationally drive the rim about its longitudinal axis.

According to the invention, the rim supporting and movement meanscomprise a sensor for measuring the mechanical strain applied to thesupporting and movement means as a result of the mechanical stress thetire bead is subjected to during tire mounting and removal on and fromthe rim. Said sensor being configured to make available a signalrepresenting the mechanical strain applied to the tire bead during tiremounting and removal on and from the rim.

Preferably, the apparatus according to the invention comprises anelectronic control unit connected at least to the sensor in order toreceive a signal relative to the mechanical strain applied to thesupporting and movement means and configured to elaborate a signalrepresenting the mechanical strain applied to the bead.

The loads applied to the tire bead during mounting and removal can bemeasured in a particularly reliable and precise manner.

This makes it possible to generate a feedback signal when the measuredstrain reaches a predetermined reference value, said signal enabling theoperator to promptly interrupt the mounting or removal process beforedamage is done to the tire bead or at least to realize the risk ofdamage and thus give the possibility of scrapping a potentially damagedtire.

Further, the invention allows control (for example, feedback control) onthe rotation of the rim and/or on the movement of the mounting/removingtool interacting with the rim to be activated according to the measuredvalues of the mechanical strain applied to the bead itself.

The invention contemplates the use of different sensors for measuringdifferent types of mechanical strain applied to the tire bead duringmounting and removal, coupled to the means for supporting and moving therim (that is, the wheel) and/or associated with tools for engaging anouter circular edge of a rim so as to be interposed between the edge anda tire bead during mounting.

Each sensor is suitable for measuring a particular type of mechanicalstrain applied to the tire bead.

In light of the above, the invention contemplates the provision of anelectronic control unit connected to all the sensors and programmed toprocess (and potentially monitor) the data received in order to deriveparameters especially representative of the actual mechanical stress(i.e. the mechanical strain) the tire bead is subjected to during itsmounting or removal.

The possibility of generating alerting signals or of applying the abovementioned types of control (on the mounting/removing tool that interactswith the bead or on the means that turn the wheel) according to theseparameters allows particularly precise and effective monitoring of themechanical stress the tire bead is subjected to and also reduces therisk of interrupting or slowing down the mounting or removal processunless strictly necessary.

Indeed, if a measured quantity does not effectively represent the realmechanical stress the bead is subjected to, the risk is that of notnoticing real damage done to the tire or, on the contrary, of takingaction in response to presumed tire damage when in fact the tire has notbeen damaged.

BRIEF DESCRIPTION OF THE DRAWINGS

Further features and advantages of the invention are more apparent inthe non-limiting description which follows of a preferred butnon-exclusive embodiment of an apparatus and method for mounting andremoving tires on and from respective wheel rims, as illustrated in theaccompanying drawings, in which:

FIG. 1 is a perspective view of an apparatus for mounting and removingtires on and from respective wheel rims;

FIG. 2 is an enlarged perspective view of a portion of the apparatus ofFIG. 1 showing the means for turning the wheel;

FIG. 3 is an enlarged perspective view of another portion of theapparatus of FIG. 1 showing the means for turning the wheel;

FIG. 4 is an enlarged perspective view of a detail of the portion of theapparatus of FIG. 1 relating to the means for turning the wheel, in apartly open view;

FIG. 5 shows a wheel having applied to it a tool for engaging a rim edgeand used in the apparatus of FIG. 1 during the mounting of the tire;

FIG. 6 illustrates a tool like the one of FIG. 1 for engaging a rimedge, according to another embodiment.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

With reference to the accompanying drawings, the numeral 1 denotes inits entirety an apparatus for mounting and removing tires 2 on and fromrespective wheel rims 3.

The apparatus 1 comprises means 4 for supporting and moving a rim 3,designed to hold the rim 3 to the apparatus 1 and to drive itrotationally about its longitudinal axis.

In light of this, the supporting and movement means 4 comprise a rim 3rotation member 171 for turning the rim 3 and the tire 2 about saidlongitudinal axis.

More in detail, the supporting and movement means 4 comprise a rotaryshaft 213 extending (vertically in the example illustrated buthorizontally in other possible embodiments) from a base 6 andoperatively connected to the rotation member 171 housed in the base 6.

At the top of the shaft 213 there extends a self-centering device 222 inthe form of a plate 7 for coupling to a rim 3, designed to anchor therim 3 (that is, the wheel) to the apparatus 1 and operatively connectedto the motor 182 to rotate about an axis of extension of the shaft 213itself.

The base 6 consists of a frame 192 having a substantially box-like shapeto contain the motor 182.

With reference to FIG. 2, the rotation member 171 comprises a motor 182connected to its rotary shaft 212 in order to drive it rotationally.

Preferably, the motor 182 is movably coupled to the frame 192 so it canmove relative to the latter; more specifically, it is mounted in apendular manner relative to the frame 192.

The rotation member 171 also comprises a supporting flange 202 equippedwith a first portion 202 a rigidly anchored to the frame 192 and asecond portion 202 b opposite the first and designed to support themotor 182 in oscillating manner.

That way, the motor 182 can oscillate about a point of connection to thesecond portion 202 b of the flange 202.

With reference to FIG. 3, it should be noted that preferably the shaft212 is kinematically coupled (for example by pulleys) to a geared motor;this geared motor (of per se known type) is connected to the shaft 213to drive it rotationally about the longitudinal axis.

According to the invention, the supporting and movement means 4 comprise(more specifically, the rotation member 171 comprises) a sensor 252 formeasuring the mechanical strain applied to the tire 2 while the latteris being mounted on, and removed from, the rim 3.

More specifically, the rim 3 supporting and movement means comprise thesensor 252, which is designed to measure the mechanical strain appliedin forced reaction to the supporting and movement means 4 as a result ofthe mechanical stress the tire 2 bead 2 a is subjected to during tiremounting and removal on and from the rim 3.

According to a first aspect of the invention, the sensor 252 isassociated with the motor 182 (or rather, to a casing of the motor) inorder to measure in particular the tangential strain applied to the tire2 bead 2 a during tire mounting and removal on and from the rim 3.

Preferably, the motor 182 is mounted in pendular manner to a frame 192(or mounted in any other way that enables the motor 182 to oscillatewith respect to the frame 192), the sensor 252 being associated with acasing of the motor 182 and with the frame 192 in order to measure themechanical strain applied to the motor as a result of the mechanicalstress the tire 2 bead 2 a is subjected to during mounting/removal ofthe tire 2 on and from the rim 3.

More specifically, the supporting means 4 comprise (that is, therotation member 171 comprises) a flange 202 for supporting the motor182. Preferably, the sensor 252 is associated with the flange 202.

The flange 202 preferably has a first portion 202 a rigidly associatedwith the frame 192 and a second portion 202 b for supporting the motor182, which supports the motor 182 in such a way that the motor canoscillate, the sensor 252 being interposed between the first portion 202a and the second portion 202 b of the flange 202.

Preferably, the sensor 252 is a load cell interposed between the firstand the second portion of the flange 202 in order to measure theoscillating movements of the motor 182, corresponding to the strainapplied tangentially to the bead 2 a of the tire 2 by the movementelement 9 interacting with the bead 2 a during removal/mounting of thetire 2.

Thus, the sensor 252 is operatively associated with a casing of themotor 182 and with the frame 192 to measure the strain applied to themotor as a result of the mechanical stress on the bead 2 a of the tire 2during mounting/removal of the tire 2 on/from the rim 3.

In effect, the rotation imparted to the shaft 213 by the motor 182,causes tangential strain to be applied to the tire 2 due to theretaining action of the bead 2 a. In other words, in the process ofmounting/removing the tire 2, the rim 3 is turned and all the stresseson the tire 2 are transferred to the shaft 213 and thus also to therotation member 171 as a whole (and to the motor 182 in particular).

Consequently, as the rotation rim 3 and the respective tire 2 turn, thesensor 252 measures the oscillating movements of the motor 182 due tothe mechanical strain applied tangentially to the bead 2 a.

For precisely measuring the movements of the motor 182, the sensor 252is advantageously interposed between the first portion 202 a and thesecond portion 202 b of the flange 202. Preferably, the sensor 252 is aload cell (of per se known type and therefore not described in detail).

According to another aspect of the invention, the sensor 252 isassociated directly with the shaft 213 through a bush 232 associatedwith the frame 192 and within which the shaft 213 slides (see FIG. 4).

It should be noted that the technical solution just described may beused alternatively, instead of the one described previously (where thesensor 252 is positioned between the motor 182 and the frame 192) or,advantageously, in combination with it.

The bush 232 contains a series of bearings that slide on the rotaryshaft 213. Preferably, the apparatus 1 comprises a plurality of sensors252 operatively coupled to said bearings.

Thus, through the bearings, the sensor 252 measures the forces andmoments acting on the shaft 213 and corresponding to the strain on thetire 2 during mounting/removal of the tire 2 itself.

The sensors 252 consist preferably of load cells and, more preferably,of multi-axis load cells.

Rising from the base 6 there is a supporting column 8 on which means formoving the tire and systems for controlling the apparatus 1 arepositioned.

In particular, the column 8 supports at least an element 9 for moving abead 2 a of the tire 2.

More specifically, the tire 2 has two beads 2 a in the form of annularedges forming the ends of the tire 2.

The movement element 9 operates between the tire 2 and the rim 3 inorder to insert the bead 2 a into an annular groove (not illustrated inthe accompanying drawings) formed in a cylindrical lateral surface ofthe rim 3. This is the case when the tire 2 is mounted on the rim 3.

It should be noted that the movement element 9 is also designed to movethe bead 2 a away from the rim and/or to hold it away from the same,that is, to place the bead 2 a in an extracted position relative to(that is to say, away from) the edge 3 a of the rim 3. This is the casewhen the tire 2 is removed from the rim 3.

Looking in more detail, the movement element 9 comprises a convenientlypower-driven supporting arm 10 extending substantially along alongitudinal axis parallel to the axis of the shaft 213 (vertical in theexample illustrated) and positioned at a predetermined distance from thesupporting means 4, on the opposite side with respect to the wheeloperatively associated with the supporting means 4.

The arm 10 supports a tool 11 designed to operate on the tire 2 byretaining a part of its bead 2 a.

As shown in the accompanying drawings, the tool 11 comprises a hook 12,or a lever 12 or any other element shaped in such a way that it can beinterposed between the bead 2 a and the rim 3 in order to clutch andextract the bead 2 a (when removing) or press it (when mounting). (Theelement will hereinafter be referred to as lever 12, without therebylimiting the scope of the invention.)

The lever 12 (that is, the tool) is operatively coupled to a respectivemovement element 13 that moves the lever 12 itself. That way, the lever12 can be inserted between the tire 2 and the rim 3 and moved to retaina part of the bead 2 a. In other words, the lever 12 acts as a gripperfor holding a part of the bead 2 a.

Preferably, as better illustrated in FIG. 1, the column 8 also supportsa bead loosening tool 14 in the form of a rotatable disc 15 designed tobe placed on a sidewall (that is, on a lateral portion) of the tire 2 insuch a way as to press it towards the opposite sidewall.

The rotatable disc 15 is supported by a power-driven arm 16 designed tomove the disc 15 to the required position. As the rim 3 and therespective tire rotate, the disc 15 enables the bead 2 a to be pushedinto an outer circular edge 3 a of the respective rim 3. During tireremoval, the bead loosener 14 is also designed to detach the bead 2 a ofthe tire 2 from the respective annular groove in the rim 3.

The apparatus 1 preferably also comprises an electronic control unit 29(illustrated schematically in FIGS. 4 and 5).

The electronic control unit 29 is connected to the sensor 252 forreceiving the data measured by it.

The electronic control unit 29 is programmed to receive and process thedata relating to the mechanical strain applied to the bead 2 a of thetire 2 during the latter's mounting on/removal from the rim 3.

Preferably, the electronic processing unit is connected to indicatingmeans adapted to provide the user with a warning signal, for examplevisual or audible, when the strain value exceeds a predeterminedthreshold.

Preferably, the electronic unit 29 is programmed to control the bead 2 amovement element 9 and/or the rim 3 supporting means 4 according to thedata received from the sensor 252. That way, the action on the tire 2 isconstantly monitored, preventing the bead 2 a from being excessivelydeformed and thus avoiding damage to the tire 2 as a whole.

In particular, the electronic unit 29 is connected to an actuator (notillustrated in the drawings because it is of known type) adapted to movethe power-driven arm 10 and/or the lever movement element 13 to drivethem according to the signal received from the sensor 252, so that thestrain measured by the sensor 252 remains under a predetermined criticalvalue (thanks to a feedback control well known in the field of automaticcontrols).

Preferably, the electronic unit 29 is connected (in addition to or,alternatively, instead of the actuator) to the motor 182 used torotationally drive the shaft 212, and hence the shaft 213, in order todrive it according to the signal received from the sensor 252, so thatthe strain measured by the sensor 252 remains under a predeterminedcritical value (thanks to a feedback control well known in the field ofautomatic controls).

In use, for mounting the tire 2 on the rim 3, the rim 3 is first placedon the rotatable mounting means 4. Next, the tire 2 is placed on the rim3 and a first bead 2 a is inserted into the annular groove of the rim 3.

At this point, the movement element 9 is used to engage a first portionof the lateral bead 2 a and to bend it past the edge 3 a of the rim 3 soas to move the portion closer to the annular groove.

An engagement tool (not illustrated since it is of known type) can nowalso be coupled to the circular edge 3 a of the rim 3 to hold the tire 2bead 2 a in place.

That way, the rim 3 and the tire 2 coupled to it can then be turned,making the movement element 9 (in particular the lever 12) slide alongthe bead 2 a. This rotational movement progressively forces the entirebead 2 a into the annular groove of the rim 3.

As the rim turns, the bead undergoes deformation and therefore the loadsacting on the tire bead 2 a are measured by the sensor 252 through theoscillation of the motor 182.

In effect, the mechanical strain applied to the tire 2 in the zone ofthe bead 2 a in contact with the lever 12 are transferred to the shaft213 and constantly measured by the sensor 252.

It should be noted that the sensor 252 measures the strain on the tire 2during the entire step of turning the rim 3 while the bead 2 a movesprogressively into the annular groove.

Thus, the sensor 252 sends to the electronic processing unit 29 aplurality of signals representing the mechanical strain. Advantageously,the unit 29 controls, according to these signals, the step of insertingthe bead 2 a and the step of turning the rim 3.

This invention therefore also provides a method for mounting a tire 2 ona respective rim 3, comprising the following steps:

-   -   positioning the rim 3 on rotatable supporting means 4;    -   positioning the tire 2 on the rim 3;    -   inserting, by means of a movement element 9, at least a first        portion of a tire 2 bead 2 a into an annular groove formed in a        cylindrical lateral surface of the rim 3;    -   turning the rim 3 and the bead 2 a in such a way that the        movement element 9 slides over the bead 2 a in order to insert        the bead 2 a itself into the annular groove;    -   measuring the mechanical strain applied to the bead 2 a of the        tire 2.

Preferably, the mechanical strain applied to the tire 2 is measured bymeans of a measuring sensor 252 associated with the rotation member 171.

Further, the mechanical strain applied to the tire 2 is measured duringthe entire duration of the step of turning the rim 3, in order tomonitor the strain applied to the tire 2 bead 2 a as the bead 2 a isprogressively inserted into the annular groove.

Preferably, measuring the mechanical strain applied to the tire 2comprises the following sub-steps:

-   -   sending a signal representing the mechanical strain to an        electronic processing unit 29;    -   controlling the step of inserting the bead 2 a and/or the step        of turning the rim 3 in such a way that the mechanical strain        does not exceed a reference value, driving means for moving a        bead 2 a movement element 9 and/or a rim 3 supporting shaft 213,        respectively, according to said signal.

This invention also provides a method for removing a tire 2 from arespective rim 3, comprising the following steps:

-   -   positioning the rim 3 with the tire 2 on it on rotatable        supporting means 4;    -   extracting, by means of a movement element 9, at least a first        portion of a tire 2 bead 2 a from an annular groove formed in a        cylindrical lateral surface of the rim 3;    -   turning the rim 3 and the bead 2 a in such a way that the        movement element 9 slides over the bead 2 a in order to extract        the bead 2 a itself from the annular groove;    -   measuring the mechanical strain applied to the bead 2 a of the        tire 2.

Preferably, the mechanical strain applied to the tire 2 is measured bymeans of a measuring sensor 252 associated with the rotation member 171.

Further, the mechanical strain applied to the tire 2 is measured duringthe entire duration of the step of turning the rim 3, in order tomonitor the strain applied to the tire 2 bead 2 a as the bead 2 a isprogressively extracted from the annular groove.

Preferably, measuring the mechanical strain applied to the tire 2comprises the following sub-steps:

-   -   sending a signal representing the mechanical strain to an        electronic processing unit 29;    -   controlling the step of extracting the bead 2 a and/or the step        of turning the rim 3 in such a way that the mechanical strain        does not exceed a reference value, driving means for moving a        bead 2 a movement element 9 and/or a rim 3 supporting shaft 213,        respectively, according to said signal.

Advantageously, the sensor 252 directly associated with the bead 2 ameasures the loads applied to the tire 2 accurately and continuously.

Indeed, the sensor 252 can measure the mechanical strain applieddirectly to the tire 2 bead 2 a while it is being turned in order tomount it on, or extract it from, the rim 3. This advantage is possiblethanks to the position of the sensor 252, which measures the tangentialstrain transferred to the motor 182.

As a result, the information collected is complete and refers to thetangential strain the bead 2 a of the tire 2 is subjected to.

Further, the structure of the entire apparatus 1 and of the means formeasuring the loads on the tire 2 are particularly simple, practical andeconomical.

According to another aspect of this invention, a sensor 251 designed tomeasure the mechanical strain applied to the tire bead by the tool 11 isassociated with the above mentioned bead 2 a movement element 9.

In light of this, the apparatus 1 (for mounting and/or removing thetire) comprises the sensor 251 (in turn preferably comprising aplurality of sensors, such as extensometers for example) coupled to thearm 10 of the movement element 9.

In this case, extensometers coupled to the outside surface of the arm 10are preferably used.

Preferably, the sensors 251 (for example, extensometers) are positionedon the outside surface at equal angular intervals; more preferably,there are three extensometers equally spaced from each other.

In light of this, the arm 10 preferably comprises a rod-shaped elementwhose cross section has the shape of a polygon (preferably regular) withat least three sides; more preferably, the polygon has an even number ofsides; more preferably still, the polygon has at least two pairs ofparallel sides.

It should be noted that the sensors 251 might also be positioned on aportion of the arm 10 whose cross section has any shape, for examplecircular.

It is stressed that the fact that the tool supporting arm is equippedwith the sensors 251 means that it can advantageously be used on both atire mounting machine and on a tire removing machine; in the exampleillustrated, the apparatus can be used to both mount and remove thetire.

Thus, the method according to the invention also comprises the furtherstep of measuring mechanical strain applied, when the movement element 9operates on the tire 2 bead 2 a, by a tool 11 of the movement element 9to the tire 2 bead (2 a), using a sensor 251 coupled to an arm 10 of themovement element 9.

According to another aspect of this invention, the apparatus 1 alsocomprises an engagement tool 17 that can be associated with the outercircular edge 3 a of the rim 3 so as to be interposed between the edge 3a and the bead 2 a of the tire 2 when the tire 2 is being mounted.

In light of this, the apparatus 1 comprises a sensor 25 associated withthe engagement tool 17 designed to measure the mechanical strain appliedby the engagement tool 17 to the bead 2 a of the tire 2 while the latteris being mounted on the rim 3.

Thus, the method according to the invention also comprises the followingfurther steps:

-   -   associating an engagement tool 17 with a circular outside edge 3        a of the rim 3 in such a way that at least a portion of the        engagement tool 17 is interposed between the edge 3 a and at        least a portion of the tire 2 when the tire 2 is being mounted;    -   measuring the mechanical strain applied to the bead 2 a of the        tire 2 by the engagement tool 17, using a sensor applied to the        engagement tool 17.

Two types of engagement tool 17 are contemplated, advantageouslyapplicable jointly to the rim 3 when the tire 2 is mounted.

The first type of engagement tool 17 (illustrated in FIG. 5) comprises amain body 18 having a clamp that can be engaged with the edge 3 a of therim 3 in a zone where the bead 2 a is operatively positioned at anannular groove in the rim, the sensor 25 being associated with theclamp.

The second type of engagement tool 30 (illustrated in FIGS. 5 and 6)comprises an elastic element 31 having an arcuate profile and forming acavity 32 that fits an arcuate portion of the edge 3 a of the rim 3, thesensor 25 being coupled to a zone of the elastic element 31 that isoperatively interposed between the bead 2 a and the edge 3 a of the rim3, when the tool 30 is coupled to the rim 3.

Preferably, the electronic processing unit 29 is connected to thesensors 25 and, where present, also to the sensors 251 and, wherepresent, also to the sensors 252 described above.

In light of this, the electronic processing unit 29 is programmed toreceive signals from two or more sensors (any combination of the sensors25, 251 and 252) to process the information captured by the sensors andderive the reference parameter values.

These reference parameters are used to obtain an optimizedrepresentation of the mechanical strain applied to the bead during tiremounting and removal.

Advantageously, the sensor 251 directly associated with the bead 2 ameasures the loads applied to the tire 2 accurately and continuously.

Indeed, the sensor 251 can measure the mechanical strain applieddirectly to the tire 2 bead 2 a while it is being deformed in order tomount it on, or extract it from, the rim 3. This advantage is possiblethanks to the position of the extensometers 251 a, which measure thestrain on the arm 10 that may be bending, pulling, compressional andtorsional strain.

As consequence, the information gathered (detected) are particularlycomplete and are pertinent to axial stresses, radial stresses,tangential stresses to which the bead of tire is subjected.

Further, the structure of the entire apparatus 1 and of the means formeasuring the loads on the tire 2 are particularly simple, practical andeconomical.

Another advantage of the invention is that it provides an apparatus anda method for mounting and removing tires that makes it possible tomeasure all types of mechanical strain applied to the tire bead (duringboth mounting and removal of the tire).

This result is obtained also thanks to the presence of the sensorscoupled to different parts of the apparatus.

Thus, the invention contemplates the use of sensors 25 in the engagementtools 17 (also, two or more of these accessories, preferably ofdifferent types, that is to say, one equipped with a clamp and anotherequipped with an elastic element 31, may be used simultaneously).

These engagement tools 17 equipped with pressure sensors 25 areparticularly suitable for measuring radial strain (especially theengagement tool 17 with the elastic element 31) and axial strainespecially the engagement tool 17 with the clamp).

The invention also contemplates the use of sensors 251 associated withthe arm 10 that supports the mounting/removing tool 11.

The sensors 251 are particularly suitable for measuring the bending,pulling and compressional strain, as well as torsional strain applied tothe arm.

Therefore, the sensors 251 make it possible to obtain information aboutall the types of strain (axial, radial and tangential) from the measuredstrain values using appropriate calculations.

The invention also contemplates the use of sensors 252 associated withthe means 4 for supporting (and moving) the rim.

The sensors 252 are particularly suitable for measuring the tangentialand axial strain on the bead.

In light of this, the integrated use of the different sensors 25, 251and 252 is particularly advantageous.

Hence, the present invention makes available an engagement tool 17 thatcan be associated with an outer circular edge 3 a of a wheel rim 3 so asto be interposed between the edge 3 a and a bead 2 a of a tire 2 of thewheel in an apparatus 1 for mounting the tire on the respective wheelrim, said engagement tool 17 for engaging the edge 3 a of the rim 3comprises a sensor 25 designed to measure the mechanical strain appliedto the tire 2 by the engagement tool 17 while the tire 2 is beingmounted on the rim 3.

Furthermore, the present invention makes available an apparatus 1 formounting and removing a tire 2 on and from a respective rim 3,comprising:

-   -   an element 9 for moving a bead 2 a of the tire 2 in order to        insert/remove the bead 2 a into/from a respective groove in the        rim 3, the element 9 comprising a tool 11 connected to a        respective supporting arm 10 for moving the bead 2 a;    -   means 4 for supporting and moving the rim 3, rotatable in such        manner as to turn the rim 3 and the tire 2 about a corresponding        longitudinal axis of the rim 3;    -   a sensor 251 associated with the supporting arm 10 for measuring        the mechanical strain applied to the bead 2 a of the tire 2 when        the latter is mounted on, and removed from, the rim 3.

What is claimed is:
 1. An apparatus for mounting and removing a tyre onand from a respective rim, comprising: a column; at least a movementelement for moving a bead of the tyre, having a tool connected to arespective power-driven arm supporting the tool, wherein the movementelement is supported by the column; a rotatable support for supportingand moving the rim, rotatable in such manner as to turn the rim and thetyre about a corresponding longitudinal axis of the rim; at least onesensor associated with the arm supporting the tool for measuringmechanical strain applied to the bead of the tyre when the tyre bead ismoved by the movement element during a rotation of the rim, wherein thearm includes a rod-shaped element having a first end connected to thecolumn and a second end connected to the tool, and wherein said at leastone sensor is coupled to said rod-shaped element, between the first andthe second end.
 2. The apparatus according to claim 1, wherein the toolis a tool for inserting/removing the bead into/from a respective groovein the rim, and wherein the at least one sensor is associated with thearm for measuring the mechanical strain applied to the bead of the tyrewhen the latter is mounted on, and removed from, the rim.
 3. Theapparatus according to claim 1, wherein the tool has a hook or a levershaped in such a way that it can be interposed between the bead and therim in order to clutch and extract the bead.
 4. The apparatus accordingto claim 1, wherein the tool is a bead loosening tool in the form of arotatable disc designed to be placed on a sidewall of the tyre in such away as to press it towards an opposite sidewall, wherein the disc issupported by said power-driven arm.
 5. The apparatus according to claim1, wherein the at least one sensor comprises a plurality ofextensometers located on an outside surface of the arm.
 6. The apparatusaccording to claim 1, wherein the arm has a cross section in the form ofa polygon with an even number of sides and therefore has an even numberof respective faces, pairs of extensometers being associated withrespective pairs of parallel faces of the arm.
 7. The apparatusaccording to claim 6, wherein the arm comprises a first end, directedtowards the rotatable support and associated with the tool, and a secondend, opposite the first end, operatively connected to a supportingcolumn, the sensor being interposed between said first and second ends.8. The apparatus according to claim 1, wherein said at least one sensoris a force sensor.
 9. The apparatus according to claim 1, comprising anelectronic control unit connected to the at least one sensor in order toreceive a signal representing the mechanical strain applied to the beadand measured by the at least one sensor, the electronic control unitbeing programmed to process the signal and provide a user of theapparatus with an indication as to the mechanical strain the bead issubjected to.
 10. The apparatus according to claim 1, comprising anelectronic control unit connected at least to the sensor in order toreceive a signal representing the mechanical strain applied to the beadand measured by the at least one sensor, the electronic control unitbeing programmed to process the signal and drive the bead movementelement and/or the rim rotatable support according to the data measuredby the sensor.
 11. A method for mounting and removing a tyre on and froma respective rim, comprising the following steps: positioning the rimand the tyre on a rotatable support; actuating a movement elementsupported by a column and having an arm for supporting a tool designedto interact with at least a portion of a bead of the tyre in such a wayas to place said portion at a predetermined position relative to therim, wherein the arm includes a rod-shaped element having a first endconnected to the column and a second end connected to the tool; turningthe rim and the tyre in such a way that the movement element slides overthe bead in order to insert or extract the bead itself into or from arespective groove in the rim; measuring mechanical strain applied to thebead of the tyre at a zone of the bead that is operatively in contactwith the movement element during tyre mounting and/or removal, using asensor associated with (i) said rod-shaped element of the arm of themovement element, between the first and the second end, and/or (ii) anengagement tool engaged with a circular outside edge of the rim, throughjaws that lock the rim edge there between during a rotation of the rim,in such a way that at least a portion of the tool is interposed betweenthe edge and at least a portion of the tyre, while the rim and the tyreare turned in such a way that the movement element slides over the beadin order to insert the bead itself into the groove, wherein theengagement tool is provided with a portion for pushing the bead of thetyre towards an annular groove of the rim.
 12. The method according toclaim 11, wherein the mechanical strain applied to the tyre is measuredduring the entire duration of the step of turning the rim, in order tomonitor the strain applied to the tyre bead as the bead is moved to thepredetermined position relative to the rim.
 13. The method according toclaim 11, wherein measuring the mechanical strain applied to the tyrecomprises the following sub-steps: sending a signal representing themechanical strain to an electronic processing unit; controlling the stepof inserting the bead and/or the step of turning the rim in such a waythat the mechanical strain does not exceed a reference value, drivingmeans for moving a bead movement element and/or rim supporting shaft,respectively, according to said signal.